Replaceable defrost heater for fin and tube evaporator and spring retaining clip for same

ABSTRACT

Spring retaining clips maintain an electrical heating wire in contact with the side edges of the fins in a fin and tube refrigeration evaporator coil. The U-shaped spring retaining clips project within the spaced fins with the free ends grasping opposed sides of a longitudinally extending tube carried by the right angle, spaced heat transfer fins.

United States Patent [191 Perez 11 3,783,635 1 Jan. 8, 1974 REPLACEABLE DEFROST HEATER FOR FIN AND TUBE EVAPORATOR AND SPRING RETAINING CLIP FOR SAME [75] Inventor:

[73] Assignee: Dunham-Bush, Inc., Harrisonburg,

[22] Filed: July 25, 1972 [21] Appl. No.: 275,005

John L. Perez, Bridgewater, Va.

[52] US. Cl. 62/276, 24/261 B, 165/64,

21-9/530, 219/531, 219/532, 219/537, 219/540 [51] Int. Cl B25b 27/14 [58] Field of Search 219/530, 531, 532,

B, 261 WL [56] References Cited UNITED STATES PATENTS 2,529,215 11/1950 Hicke 62/276 X 3,063,253 11/1962 Dickson et a1 62/276 X 3,099,914 8/1963 De Witt et al. 62/276 1,176,210 3/1916 Farley 24/139 X 1,222,510 4/1917 Zirkle 24/139 1,446,362 2/1923 Vogel 24/261 2,687,626 8/1954 Bartlowe 62/276 2,749,717 6/1956 Duncan et a1. 62/276 X 2,819,858 l/l958 Mittendorf 148/54 3,343,596 9/1967 Kritzer 165/67 3,691,348 9/1972 Kunz 219/532 FOREIGN PATENTS OR APPLICATIONS 561,596 8/1958 Canada 62/276 Primary Examiner-Volodymyr Y. Mayewsky Attorney-Richard C. Sughrue et a1.

[5 7 ABSTRACT Spring retaining clips maintain an electrical heating wire in contact with the side edges of the fins in a fin and'tube refrigeration evaporator coil. The U-shaped spring retaining clips project within the spaced fins with the free ends grasping opposed sides of a longitudinally extending tube carried by .the right angle, spaced heat transfer fins.

8 Claims, 2 Drawing Figures PMHMED JAN 81974 FIG] . 1 v REPLACEABLE DEFROST HEATER FOR FIN AND TUBE EVAPORATOR AND SPRING RETAINING CLIP FOR SAME BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to fin and tube evaporator coils, and more particularly to the employment of a plurality of wire spring retaining clips for removably coupling an electrical heater wire to the side edges of the evaporator coil heat transfer fins.

2. Description of the Prior Art Refrigeration systems for cooling food storage rooms such as meat coolers, are constructed in conventional fashion with a plurality of longitudinally extending spaced rows of refrigerant carrying tubes supported by longitudinally spaced, thin stamped metal fins which define an elongated, rectangular assembly. Air is forced to pass through the spaced fins at right angles to the axis of the tubes carrying the refrigerant.

1 In order to periodically remove the solidified condensate on the exterior surface of the tubes and on the fins supporting the same, stainless steel sheathed electric heaters constituting essentially resistance wire heaters are conventionally inserted through longitudinally aligned openings or holes in the fins and, upon energization of the heaters, the heat spreads readily through the wires to the tubes to melt the solidified condensate.

Of necessity, the replacement of the electrical heater requires practically complete dismantling of the unit cooler which is time consuming and inordinately expensive.

SUMMARY OF THE INVENTION angles to the axis of the tubes and form therewith a longitudinally extending assembly. The improvement comprises a plurality of spring retaining clips which carry the electric wires in contact with the fins, with the clips inserted within the fins at longitudinally spaced positions and removably clamped to the refrigerant carrying tubes. The wires extend parallel to the direction of a tube and the edges of the fins are preferably recessed to receive the wires. The'spring retaining clips are preferably formed of spring wire, bent into U-shape, with the closed end carrying the heater wire and the open ends grasping respective sides of the refrigerant carrying tubes. Where the tubesform alternately offset, mulsponding to the radius of the pipe to readily grasp the tubes of the inner row.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT Turning to the drawings, a fin and tube evaporator coil 10 which may form a major component of a unit cooler for food storage room such as a meat cooler, frozen food locker or the like, is constituted by a rectangular formed metal tube sheet 12, at its left end, FIG. I, and being provided with a similar tube sheet at the opposite end (not shown). The evaporator coil 10 is purposely broken away at its right end to further illustrate the construction of the same. In this respect, the evaporator coil consists essentially of a plurality of refrigerant carrying tubes 14 which pass through spaced, aligned openings 16 in horizontally offset rows within the stamped thin sheet metal fins l8. Fins 18 are generally rectangular in form and support the refrigerant carrying tubes 14 at right angles to the plane of the fins. Such construction is conventional and the coils formed thereby are conventionally known as fin and tube heat exchangers. It is essential only to note that the expansion of liquid refrigerant within the tubes 14 which changes from liquid state to gaseous state, absorbs heat from the air surrounding the same. The moisture in the air condenses on the evaporator coil 10, covering the surfaces of the fins and the tubes and may build up to the point where the frozen condensate actually prevents or greatly impairs the passage of air through the fins and around the tubes. Periodically, therefore, means must be employed to defrost this condensate.

In the presentinvention, this is'achieved by a stainless steel sheathed electric heater which comprises spaced parallel heater wires indicated 20. The small diameter wires 20 extend parallel to the refrigerant carrying tubes 14 and adjacent to win contact with leading side edges 22 of the heat conducting fins l8. Preferably, the tube sheet 12 is slotted at 24 and the edges 22 of fins 18 are likewise slotted as at 26, permitting the heater wires 20 to be located in excellent heat contact position with respect to the fins and, in this case, just outside the first row of refrigerant carrying tubes 14. It is noted that the illustrated evaporator coil 10 is provided with three parallel rows of vertically spaced refrigerant carrying tubes 14 with the tubes of a given vertical row horizontally offset from the tubes of the adjacent row. The inner row of tubes is offset such that its tubes are centered between the tubes of the first row, and spaced rearwardly from the leading edge 22 of the fins 18 to a greater extent than that of the first row of tubes 14. In this respect, the electrical heater wires 20 are in horizontal alignment with respective tubes of the intermediate row of tubes as defined by the slots or recesses 26 within the edges 22 of the fins 18.

The present invention is particularly directed to the employment of a plurality of spring wire retaining clips indicated generally at 28, which project into the slots defined by spaced fins 18 to insure the positioning and maintaining of the heater wires 20 within slots 26 of the fins 18. In this respect, the spring wire clips 28 are preferably formed of stainless steel spring wire on the order of 0.10 inch diameter. They are generally U-shaped in configuration as evidenced in FIG. 2, consisting of a base 30 and a pair of legs 32 which are crossed as at 34 adjacent the base to provide the desired resiliency to the spring clips. The legs 32 adjacenttheir free ends are provided with opposed, concave curved portions 36 and terminate in outwardly flared ends 38. The curved portions 36 are spaced or separated in the relaxed state somewhat less than the outside diameter of the refrigerant carrying tubes 14. The spacing between the legs 32 adjacent the cross over point 34 is generally on the order of the diameter of the electrical heater wires 20, such that the wires 20 are closely embraced by the clips adjacent base 30, with the legs at this point maintaining the wires 20 within the fin slots 26. The wires 20 are prevented from moving out of the slots 26 in the absence of release of the free ends of the clip from their respective tubes 14 of the intermediate row of tubes. The means for electrically connecting the heater wires 20 in series or in parallel or for energizing the same, as well as the components of the refrigeration system supplying refrigerant to tubes 14 have purposely been eliminated from the drawing, since such means are conventional in the art. Further, while the clips are of such a length and configuration that their inner ends are I coupled to the offset, intermediate row of refrigerant carrying tubes 14, the clips may be modified to permit coupling of the same to the first row of heat exchange tubes, if desired. Further, while two longitudinally spaced clips 28 are shown in the arrangement of FIG. 1 for maintaining each defrost wire 20 within horizontally aligned slots 26 and in good heat transfer relationship to the fins supporting the same, each wire may have one or more clips 28 coupling the same to the evaporator coil 10. Further, while wires 20 are provided intermediate of each pair of the tubes of the first row, more or less wires may be employed depending upon the capacity of the wires to defrost the evaporator coil under the operating conditions of the refrigeration system. The electrical heaters 20 are described in terms of stainless steel sheathed electrical resistance heaters and illustrated schematically in terms of solid conductors, however, it is obvious that the defrost mechanism may comprise any applicable electrical resistance heater of tubular configuration and compatible with the evaporator coil and which extend in rod or wire like fashion in'contact with one edge of the multiple heat conducting fins 18. While the heaters 20 are indicated as being received within slots 26 within edges 22, of the fins 18, since the wires are surrounded by legs 32 of the wire clips, the edges 22 of the fins may be unbroken and the wires merely pressed into good heat transfer contact with the edges of the same, and lie flush with the front edge of the evaporator coil rather than internally of the fins under the bias of clips 28.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a fin and tube evaporator coil for a refrigeration system comprising a plurality of spaced parallel refrigerant carrying tubes tubes extending through closely spaced, thin metal fins, positioned generally at right angles to the axis of the tubes and forming a longitudinally extending assembly therewith, and a plurality of sheathed electric heater wires in juxtaposition to said fins and tubesfor defrosting the same. the improvement wherein:

said wires extend across the ends of said fins parallel to and spaced from said tubes, and

a plurality of U-shaped, wire spring retaining clips are coupled to said electric heater wires at spaced longitudinal positions with the outer closed ends of said U-shaped clips embracing said wires and with their free inner ends inserted within said fins and removably clamped to said tubes to maintainthe wires in heat transfer contact with said fins.

2. The fin and tube evaporator coil as claimed in claim 1, wherein said fin edges are slotted and receive said wires.

3. The fin and tube evaporator coil as claimed in claim 1, wherein said refrigerant carrying tubes form multiple rows with the tubes of one row offset from the tubes of another row and wherein said clips extend between tubes of the row closest to said edges carring said wires and are coupled to respective tubes of a succeedingrow at their inner ends.

4. The fin and tube evaporator coil as claimed in claim 2, wherein said refrigerant carrying tubes form multiple rows with the tubes of one row offset from the tubes of another row'and wherein said clips extend between tubes of the row closest to said edges earring said wires and are coupled to respective tubes of a succeedinsr wet erei ends- 5. The fin and tube evaporator coil as claimed in claim 1, wherein said U-shaped wire clips have inwardly extending legs, crossed at their closed ends to provide resiliency to the clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying tubes. j

6. The fin and tube evaporator coil as claimed in claim 2, wherein said U-shaped wire clips have in wardly extending legs, crossed at their closed ends to provide resiliency to the clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying b S- 7. The fin and tube evaporator coil as claimed in claim 3, wherein said U-shaped wire clips have inwardly extending legs, crossed at their closed ends to provide resiliency to the clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends'of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying u s. W

8. The fin and tube evaporator coil as claimed in claim 4, wherein said U-shaped wire clips have inwardly extending legs, crossed at their closed ends to provide resiliency to the-clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying tubes. 

1. In a fin and tube evaporator coil for a refrigeration system comprising a plurality of spaced parallel refrigerant carrying tubes tubes extending through closely spaced, thin metal fins, positioned generally at right angles to the axis of the tubes and forming a longitudinally extending assembly therewith, and a plurality of sheathed electric heater wires in juxtaposition to said fins and tubes for defrosting the same, the improvement wherein: said wires eXtend across the ends of said fins parallel to and spaced from said tubes, and a plurality of U-shaped, wire spring retaining clips are coupled to said electric heater wires at spaced longitudinal positions with the outer closed ends of said U-shaped clips embracing said wires and with their free inner ends inserted within said fins and removably clamped to said tubes to maintain the wires in heat transfer contact with said fins.
 2. The fin and tube evaporator coil as claimed in claim 1, wherein said fin edges are slotted and receive said wires.
 3. The fin and tube evaporator coil as claimed in claim 1, wherein said refrigerant carrying tubes form multiple rows with the tubes of one row offset from the tubes of another row and wherein said clips extend between tubes of the row closest to said edges carring said wires and are coupled to respective tubes of a succeeding row at their inner ends.
 4. The fin and tube evaporator coil as claimed in claim 2, wherein said refrigerant carrying tubes form multiple rows with the tubes of one row offset from the tubes of another row and wherein said clips extend between tubes of the row closest to said edges carring said wires and are coupled to respective tubes of a succeeding row at their inner ends.
 5. The fin and tube evaporator coil as claimed in claim 1, wherein said U-shaped wire clips have inwardly extending legs, crossed at their closed ends to provide resiliency to the clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying tubes.
 6. The fin and tube evaporator coil as claimed in claim 2, wherein said U-shaped wire clips have inwardly extending legs, crossed at their closed ends to provide resiliency to the clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying tubes.
 7. The fin and tube evaporator coil as claimed in claim 3, wherein said U-shaped wire clips have inwardly extending legs, crossed at their closed ends to provide resiliency to the clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying tubes.
 8. The fin and tube evaporator coil as claimed in claim 4, wherein said U-shaped wire clips have inwardly extending legs, crossed at their closed ends to provide resiliency to the clip, said electric heater wires are captured inside the crossed legs and forced into contact with the fins, and wherein the free ends of the legs are provided with opposed, concave curvatures grasping respective sides of said refrigerant carrying tubes. 